Attacks exploit unpatched weakness in Adobe apps

Ham-handed PDF peril from Zeus

Criminals behind the notorious Zeus crimeware package have begun exploiting an unpatched hole in the widely used portable document format to install malware on end user computers.

The booby-trapped PDF documents arrive in emails that purport to contain a billing invoice, according to a post from M86 Security Labs. If the user opens the documents and clicks through a series of dialog boxes, PDF readers from Adobe will execute a file that makes the PC a part of a botnet (The FoxIT reader will automatically save the malicious file on the user's hard drive.)

The exploit is a ham-handed exploit of a feature included in the PDF specification that allows documents to automatically run code. That's because it requires javascript to be turned on and it doesn't alter the wording of one of the dialog boxes, as security researcher Didier Stevens showed was possible.

"This is why I would classify this attack attempt as rudimentary at best, with little to no real sophistication," Jeremy Conway, another researcher who modified Stevens' attack, wrote here. "If this was the best the malicious actors have to offer we would have nothing to worry about, but I am afraid this is only the beginning and I am sure we will see far more sophisticated attempts at exploiting the Launch action in the future."

Adobe has said it is mulling changes to its Reader and Acrobat programs to close the hole. Users in the meantime can protect themselves by turning off the automatic launch feature. To do this, go to Edit > Preferences and click on Trust Manager in the left pane. Then, uncheck the box for "Allow opening of non-PDF file attachments with external applications." ®

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